Apparatus for sizing textile fibres

ABSTRACT

Apparatus for sizing slivers or rovings of textile fibres in which the slivers or rovings are unwound from a supply thereof and are accelerated progressively and smoothly to a given speed by a pulling force which is always less than the cohesion force between the fibres constituting the slivers or rovings. The slivers or rovings are then flattened by passing between a first pair of pressure rollers, before dipping into a bath of size and then passing through a second pair of pressure rollers to be forwarded onto a drier for drying the size whereafter they are wound up on a bobbin. The size has the effect of gluing the fibres of slivers or rovings together and imparts sufficient cohesion for the slivers or rovings to be worked as such in a loom or knitting machine. The size may subsequently be removed after manufacture of a textile article from the slivers or rovings.

United States Patent 1 Schutz et al.

i 1 May 27, 1975 APPARATUS FOR SIZING TEXTILE FIBRES 22 Filed: Oct. 1, 1973 [21] App]. No.: 402,031

Related US. Application Data [62] Division of Ser. No. 203,720, Dec. 1, 1971, Pat. No.

FOREIGN PATENTS OR APPLICATIONS 898,688 6/ 1962 United Kingdom 57/2.5

Primary Examiner-Mervin Stein Attorney, Agent, or Firm-DelLio and Montgomery [57] ABSTRACT Apparatus for sizing slivers or rovings of textile fibres in which the slivers or rovings are unwound from a supply thereof' and are accelerated progressively and smoothly to a given speed by a pulling force which is always less than the cohesion force between the fibres constituting .the slivers or rovings. The slivers or rovings are then flattened by passing between a first pair of pressure rollers, before dipping into a bath of size and then passing through a second pair of pressure rollers to be forwarded onto a drier for drying the size whereafter they are wound up on a bobbin. The size has the effect of gluing the fibres of slivers or rovings together and imparts sufficient cohesion for the slivers or rovings to be worked as such in a loom or knitting machine. The size may subsequently be removed after manufacture of a textile article from the slivers or rovings.

11 Claims, 3 Drawing Figures PATENTEB RAY 2 7 I975 SHEET 1 [1? Z m mm APPARATUS FOR SIZING TEXTILE FIBRES This is a division of application Ser. No. 203,720 filed Dec. 1, 1971 now US. Pat. No. 3,791,132, issued Feb. 12, 1974.

The present invention relates to an apparatus for sizing textile fibres, more particularly to apparatus for sizing textile fibres in the form of slivers or rovings, and to textile articles formed therefrom.

Conventionally, articles such as fabrics, knitwear etc., are formed with the aid of textile fibres in the form of a yarn. This yarn should have a suppleness, an elasticity and a resistance sufficient to enable it to be subjected, without damage, to the diverse constraints ccasioned by its manipulation during the course of the operations of weaving or of knitting.

For this purpose, the conventional yarn, obtained by spinning a textile raw material, is more or less twisted, in order to improve the cohesion between the fibres constituting the yarn, then, in this state is subjected to sizing, when it is intended to form the warp of a fabric.

This spinning can, in general, be divided into two successive stages which, in a number of cases present the same importance and substantially the same cost price. During the first stage, called preparation, the textile material in the form of bales is treated by heating and then by carding to give a web, the textile fibres being distributed in a homogeneous fashion and oriented preferentially in the sense of advance of the web, the latter being eventually subdivided to form slivers. These are subjected to doubling and drawing to give rovings. The slivers generally have hundreds of thousands of fibres to the section, such that the roving comprises thousands of fibres to the section; but it is possible to obtain a roving of desired fineness by suitable drawing.

During the second stage of the spinning proper, the rovings are made finer by successive drawing, until one obtains a yarn in which the number of fibres to the section can fall to less than 50. The fibres then receive a number of turns of twist to form a yarn giving the required resistance and elasticity. The yarns are then fed to a loom or knitting machine to produce the textile article.

This conventional technique of fabrication of textile articles is long and costly. Moreover, the twist of the fibres looses a large part of the ability to cover the fibres constituting the yarn.

It has already been proposed to omit the operation of the twisting of the yarn, effected usually during the second stage of the treatment of the yarn and to replace this twisting by a sizing operation.

According to a known process of manufacture, of a yarn without twist, the slivers and rovings of the textile fibres are drawn until one obtains a very thin band which is impregnated with size; then the sized fibres of this band are re-grouped in such a manner as to form a yarn of a substantially circular section which is then dried.

A known sizing apparatus for the purpose of putting into operation this process comprises in particular: a first drawing train for the slivers or rovings of textile fibres unwound from a bobbin; an endless conveyor belt for feeding the textile fibres leaving the first drawing train in the form of a very thin band to the point where they are sized; two parallel coating rollers defining between them a space sufficient to receive the size and deposit it on the walls of the band of fibres; at least one forming roller defining with one of the coating rollers a space situated on the path of the band of fibres downstream of the coating space, the said forming rollers being given an axial reciprocating motion; two guiding rollers and a second drawing train disposed on the path of the sized textile fibres downstream from the point of contact with the forming roller with the said textile fibres.

Another known installation comprises, in particular, an endless conveyor belt furnished with a layer of size and of which the upper face is put in contact with the textile fibres leaving the drawing train.

In these installations, the textile fibres are coated with size by contact with a guide surface of the fibres, this surface being covered with size.

This method of sizing has the disadvantage of transferring to the fibres an excessive quantity of size distributed in a heterogeneous fashion. Moreover, the forming rollers of these apparatuses exercise on the thin band of fibres an alternating force which can create partial or total rupture of the band of fibres and also produces irregularities in the thickness of the yarn'obtained or in the distribution of the long and short fibres in the yarn.

Furthermore, the known procedure takes away from the rovings their initial character and of necessity transforms them, by thinning, into yarns in which the fibres are glued to one another along their length.

According to one aspect of the invention, there is provided a process for sizing slivers or rovings of textile fibres, such process comprising the steps of unwinding the slivers or rovings from a supply thereof, applying a pulling force to the slivers or rovings progressively and smoothly to accelerate the slivers or rovings to a given speed, said pulling force always being less than the cohesion force between the fibres constituting the slivers or rovings; thereafter flattening the slivers or rovings; dipping the slivers or rovings into a bath of size; drying the sized slivers or rovings and winding up the sized slivers or rovings on a bobbin.

With such a process it is possible to form slivers or rovings whichlend themselves to the manufacture of textile articles of all sorts, such as net or mesh articles, knitted articles, laps, carpets or tufted articles, or interlaced articles such as fabrics, without the necessity to transform the rovings into yarns.

Thus, the slivers or rovings are constituted by fibres glued partially to one another to acquire the necessary cohesion to be worked without substantial deformation. Moreover, such slivers or rovings lend themselves without difficulty to the operations of weaving or knitting. The qualities of the textile article formed from the slivers or rovings temporarily consolidated are fully evident after elimination of the size once the article is manufactured.

These articles present then an exceptionally soft touch, a great suppleness, apparent increased volume and can be thermally insulating and have a brilliance considerably superior to textile articles formed from a conventional yarn.

Because the sized slivers or rovings can be utilized directly on looms or knitting machines, one saves, for a textile article formed from rovings according to the invention, at least the cost price of the transformation of the rovings into a twisted yarn or cable.

The invention also provides apparatus for forming sized slivers or rovings, such apparatus comprising a frame having a feed bobbin for slivers or rovings mounted for free rotation substantially without friction therein; a vat of size, a first pair of pressure rollers mounted between said feed bobbin and said vat, a second pair of pressure rollers mounted downstream of said vat of size, a drier mounted downstream of said second pair of rollers, a windup bobbin positioned to receive slivers or rovings from said dryer and drive means to drive at least one of the rollers of each of said pairs of pressure rollers at a controlled speed. Thus, the slivers or rovings can be accelerated progressively and smoothly and the pulling force does not exceed the natural cohesion force of the fibres and can be dipped into the bath of size without the fibres being pressed one against the other and without the initial regularity of the rovings being destroyed.

Finally, the invention provides a textile article formed from slivers or rovings, which may be produced by using the apparatus of the invention, and the slivers or rovings having fibres which are not heckled and have very little or no twist.

In order that the invention will more fully be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:

FIG. 1 shows schematically one embodiment of apparatus according to the invention;

FIG. 2 represents schematically the drive device for the pressure rollers and for the rollers of the drier; and

FIG. 3 is a perspective view of the rollers of the drier of the apparatus.

In FIG. 1, the feed bobbin 1 on which are wound slivers or rovings 2, is mounted so as to be freely rotatable without friction on the lateral pointed and coaxial ends 3. These ends 3 are located in ball bearings 4, mounted on an intermediate support 5 disposed on a frame 6, which itself is capable of turning around an axis XX perpendicular to the axis of the bobbin 1 by means of a transmission formed by a pulley 7 associated with a drive belt 8.

The slivers or rovings 2 unwind from the bobbin 1 and pass successively between a first pair of pressure rollers 9 and 10 disposed upstream of a size bath 11, then into the latter between a second pair of pressure rollers 12 and 13 disposed downstream of the said vat 11 and then into a hot air drier 14.

The lower pressure rollers 10, 13 have smooth steel surfaces, whereas the upper pressure rollers 9 and 12 can be covered with a substance having a high coefficient of friction for example rubber to ensure a positive drive to the fibres of the roving 2 between the pairs of rollers 9, 10 and 12, 13.

The size vat 11 contains a bath of size 11a and is provided with a dip roller 15 adjustable in height to guide and totally immerse the slivers or rovings 2 in the bath 11a.

The temperature of the bath of size 1 1a is maintained constant by means of a water bath l6 heated by a resistance 17 fed through a thermostat 18 equipped with a control thermometer 19.

The pressure rollers 9 and 12 are each provided with a pressure regulator comprising a lever 20 and 21, pivoted at one end 22 and 23, and carrying respectively a bearing for the shafts 24 and 25 of the rollers 9 and 12, and at the other end weights 26 and 27 adjustable in position.

After passage between the pressure rollers 12 and 13, the sized slivers or rovings 2' enter into the hot air drier 14 through an entry opening 28 arranged laterally in the said drier 14 near its upper end.

Within the cabinet of the drier 14 are two series 29 and 30 of return pulleys 29', 29" and 30', 30", the pulleys of each series being mounted on the same shaft 31 or 32 respectively, the pulleys being so disposed that a pulley of the upper set is in the same vertical plane as the pulley on the lower set situated immediately downstream thereof.

At its lower part the drier 14 is provided with an entry opening 33, for hot air of which the temperature is regulated by a thermostat, of which only a thermometer 34 is shown in FIG. 1.

The sized and dried slivers or rovings 2 leaves the drier 14 through an outlet opening 35 provided at its lower end and is wound up on a wind-up bobbin 36, with a friction drive 37 to maintain a constant tension on the slivers or rovings 2" downstream from the drier According to one embodiment of the invention, an oiling or waxing apparatus 38 is disposed in the path of the slivers or rovings 2" between the exit 35 of the drier l4 and the rewinding bobbin 36.

One can equally, with advantage, provide an oiling or waxing apparatus 38' between the downstream pressure rollers 12, 13 and the entrance to the drier 28.

In certain cases, notably for the acceleration of the roving and when the roving is very fragile by virtue of the weak force of cohesion between its constituent fibres, it can be advantageous to provide a support and transport filament constituted preferably from a material different from that of the slivers or rovings.

In FIG. 1, this support and transport filament 39 unwinds from a bobbin 40 and is placed in contact with the slivers or rovings 2 unwinding from the bobbin 1 by means of a frusto-conical yarn guide 41, the larger base of which is directed towards bobbin 1.

The support and transport filament 39 associated with the slivers or rovings 2 passes successively between the upstream pressure rollers 9 and 10, through the sizing bath 11a between the downstream pressure rollers 12 and 13 and then into the drier 14.

The support and transport filament 39 and the sized slivers or rovings 2 are separated from one another, for example, at the moment where they reach the first pulley 30 of the lower series of pulleys 30, that is to say before the sized rovings are completely dried.

At this moment, the sized slivers or rovings 2 makes a turn around this first pulley 30' and rises towards the following upper pulley 29' while the support filament 39 leaves the drier 14 through a lower exit opening 42 and is rolled up on a rewind bobbin 43.

According to another embodiment of apparatus, the support and transport filament can be constituted by an endless filament. As shown in the drawings in dashed lines in FIG. 1, the endless support and transport filament 39 leaves the drier 14 through an exit 42 and passes successively on a drive roller 44 and on a tensioning roller 45 before joining the slivers or rovings 2 in the yarn guide 41 and continues on its path in common with the slivers or rovings 2 until the drier, where its separation with the said slivers or rovings is effected in the same manner as in the preceding embodiment.

In FIG. 2, the upstream pressure roller 9 and downstream pressure roller 12 as well as the shaft 31 of the upper series 29 of pulleys of the drier 14 are rotated by a transmission system having a relative adjustment, by a drive motor 46 having a fly wheel coupled to its rotor, the said motor 46 being, moreover, coupled to a speed variator 47 and provided with reduction gear 48.

This transmission system includes a drive belt 49 connecting the output shaft 50 on the reduction gear to the shaft 25 of the pressure roller 12. This shaft 51 is coupled firstly to the shaft 31 by a V-belt 52, which passes around pulleys 53 and 54 of which one is fixed to the shaft 25 and the other to the shaft 31, and, secondly, to the pressure roller 9 by a V-belt 55 and passing around pulleys 56 and 57 of which one is fixed to the shaft 24 and the other to the shaft 25 of the pressure roller 12. The discs of the pulleys 53, 54, 56 and 57 are of adjustable separation and define, between their bevelled peripheral faces grooves having a depth adjustable as a function of the spacing between the discs.

According to FIG. 3, each of the series of the upper pulleys 29 and lower pulleys 30 of the dryer 14 is constituted by a roller of which the first disc has a very small coefficient of friction and is anti-adhesive, the roller comprising a series of coaxial annular grooves 29, 29" and 30, 30".

The support and transport filament 39 associated with the sized slivers or rovings 2 passes on the first upper pulley 29' and separates from the sized slivers or rovings 2, for example at the moment when the said sized slivers or rovings 2' reaches the first lower pulley 30'.

In operation, the slivers or rovings 2 are progressively and smoothly accelerated by the driven rollers 9 and 12, cooperating with rollers and 13, and by the series of driven pulleys 29 of the drier 14. The force applied for this purpose on the slivers or rovings 2 is such that it remains always below the natural cohesion force of the fibres constituting the slivers or rovings 2. The pulling force is preferably below 5 to cN. The application of a weak pulling force on the slivers or rovings 2 is possible due to the motor-reduction-gear 46, 48 provided with a speed changer 47 and by virtue of the very small frictional forces exercised on the supply bobbin 1. These friction forces are, in general, less than several cN by virtue of the mounting of the bobbin 1 between the points 3 located in the ball bearings 4.

The slivers or rovings 2 are thus accelerated progressively until they reach the predetermined feed speed through the apparatus which can reach m/minute or even more.

The mounting of the bobbin 1 on the rotatable frame 5 permits removal of several turns of twist from the slivers or rovings 2. This is, for example, necessary when the slivers or rovings have been rolled on the bobbin with several turns of twist to give to the fibres of the slivers a better hold, making them suitable for initial winding. It should be understood, when one talks of a small twist, one must understand a twist of several turns per meter but this is not comparable with a normal twist comprising hundreds or even thousands of turns per meter.

The upstream pair of pressure rollers 9 and 10 flattens the slivers or rovings 2 before they are immersed in the bath of size 1112 by the dip roller 15. Thus, it is possible to force air between the fibres to increase the surface of contact between the slivers or rovings 2 and the size.

The downstream pair of pressure rollers 12 and 13 compresses the sized slivers or rovings 2 after their soaking in the bath of size 11a, thus improving the distribution of the size into the interior of the said slivers or rovings and to reject any excess size. It is possible to regulate the degree of flattening of the slivers or rovings by variation of the pressure on the rollers and to regulate the quantity of size expressed from the sized slivers or rovings 2 by an adjustment of the pressure applied by the rollers 12 and 13.

Certain textile fibres undergo, during their dampening by the size, a modification of their length in general, less than 2 percent. To take into account any such increase or decrease, the spacing between the discs of at least one of the pulleys 56, 57 can be regulated in the appropriate sense such that the upstream rollers 9 and 10 turn with a peripheral speed less than or greater than that of the downstream pulleys 12, 13. In a similar fashion, the control of the spacing of the discs of at least one of the pulleys 53, 54 permits control of the speed of movement of the sized slivers or rovings 2 between downstream pressure rollers 12, 13 and the drier 14. The temperature of the drying air in the drier 14 is in general between 40C and 150C.

The size bath 11a is of a composition adapted to the nature of the filaments of the rovings 2 and can contain a plasticising substance, the purpose of which is to give to the sized and dried slivers or rovings 2 the necessary suppleness to permit the use of the said slivers or rovings on a loom or on a knitting machine. The temperature of the size bath 11a is maintained constant and is, according to the particular size used, between 20C and C.

At the outlet to the bath of size 11a and/or of the dryer 14, the slivers or rovings are oiled or waxed, to lubricate the surface of the sized slivers or rovings. According to the particular case, this oiling operation is effected, either when the sized slivers are still wet and- /or when the sized slivers are already dry.

The support and transport fiilament 39 or 39' is sometimes necessary to support the slivers or rovings 2, at least during the beginning of the unrolling of the slivers or rovings. Nevertheless, one can, in general, interrupt the support and transport filament 39 or 39 after the unwinding of a dozen or so meters of slivers 2, unrollin g which is sufficient to obtain the speed of passage through the apparatus.

The support filament 39 is separated from the sized slivers 2' preferably, when the latter is still wet. This separation is effected, for example, in the heater 14 at the moment when the sized slivers or rovings 2 and the support filament 39 pass around the second pulley 30' of the heater 14, the pulley 30 being positioned, in the sense of movement of the slivers or rovings 2', immediately after the entry 28 into the drier 14. At the exit of the drier 14, the dried slivers 0r rovings 2" are rolled up under regulated tension on the windup bobbin 36 driven by the friction drive 37.

By way of example, there is indicated here below, the conditions in which the slivers or rovings of polyamide, and/or polyester, according to the invention, can be formed.

1. Material polyamide fibres of 1.7

dtex Length of fibres 40 mm -Continued Count of the unsized rovings 200 tex Twist several turns per meter, therefore practically no twist Upstream pressure roller 1 daN/cm force Temperature of the size bath 50C Sizing substance 5% aqueous solution of pure polyvinyl alcohol, of which the degree of polymerisation is between l7OO and 1800 Normal speed through the apparatus Pressure force of the downstream rubber pressure roller 9 on th 10 meters/minute steel roller 10 2.5 daN/cm. per

generatrix Drying air heated to 90C Rewinding tension cN/roving This polyamide roving has been worked with success by knitting at a setting of l and l on a gauge E8 (needles to the inch) machine at a tightness of 12.

2. Material polyester Count of the polyester fibres 1.7 dtex Length of the fibres 40 mm Count of the sized rovings 170 dtex Upstream pressure roller forces l daN/cm Temperature of the sized bath 50C Solution of 4% of acrylic copolymer known commercially under the name NEOCRYL 8T8 Sizing substance Downstream pressure force 2.5 daN/cm Normal speed of travel through the apparatus 20 meter/minute Drying air heated to 90C Rewinding tension ZOcN/roving (0.lcN/tex) Wool of which the fibres have a mean diameter of 10 to 20 pm 3. Material Count of the sized rovings 140 tex Upstream pressure force ldaN/cm Temperature of the size bath 50C aqueous solution of 5% of pure polyvinyl alcohol of which the degree of polymerisation is between 1700 and 1800 Sizing substance Sizing substance also comprises a solution of one one-thousandth of anti-foaming agent, known under the commercial name NOPCO 1497V.

Downstream pressure roller force 2.5 daN/cm Speed of passage through the apparatus 20 m/mlnute Drying air at a temperature between 80C and 90C.

This roving of wool has been worked with success by return stitch knitting, on gauge E6, tightness 7, 8 or 9.

Textile articles thus obtained can be treated in a bath to eliminate the size such that the fibres of the rovings recover their initial characteristics.

We claim:

1. Apparatus for forming sized slivers or rovings, said apparatus comprising, in combination:

a. a frame;

b. a feed bobbin for slivers or rovings mounted for free rotation substantially without friction in said frame;

c. a vat of size;

d. a first pair of pressure rollers mounted between said feed bobbin and said vat;

e. a second pair of pressure rollers mounted downstream of said vat of size;

f. a drier mounted downstream of said second pair of rollers;

g. a windup bobbin positioned to receive the slivers or rovings from said drier; and

h. a drive means effective to drive at least one of the rollers of each of said pairs of pressure rollers at a controlled speed.

2. Apparatus as claimed in claim 1, wherein said drier comprises a cabinet, at least two superposed sets of return pulleys within said cabinet rotatable on substantially parallel axes, the pulleys of one set being mounted on the same shaft and being located in the same vertical plane as the pulleys of the other set.

3. Apparatus as claimed in claim 1, and further comprising a support and transport filament for the slivers or rovings, means disposed between the feed bobbin and the first pair of pressure rollers for placing the support and transport filament into contact with the slivers or rovings and means to separate the sized slivers or rovings from the support and transport filament within the drier before the slivers or rovings are dry.

4. Apparatus as claimed in claim 3, wherein said means for placing the slivers or rovings in contact with the support and transport filament comprise a frustoconical yarn guide having a larger and a smaller base, the larger base being directed towards the feed bobbin and the smaller base towards the first pair of said pressure rollers.

5. Apparatus according to claim 3, wherein the means for separating the sized slivers or rovings from the support and transport filament within the drier comprise a rewind bobbin for the support and transport filament.

6. Apparatus according to claim 3, wherein the support and transport filament is endless.

7. Apparatus according to claim 1, and further com prising a pressure regulator associated with one of the rollers of each pair of pressure rollers, the other roller being mounted on a shaft having a fixed bearing.

8. Apparatus according to claim 7, wherein the pressure regulator comprises a pair of levers, one lever being associated with each pair of pressure rollers, the lever being pivoted and carrying a bearing for said one roller of each pair and supporting an adjustable weight movable along its length.

9. Apparatus according to claim 1, wherein said frame is itself mounted for rotation about an axis perpendicular to the axis of the feed bobbin.

10. Apparatus according to claim 2, wherein the pu lleys of the drier comprise a roller provided with axially spaced apart annular grooves of the same depth.

11. Apparatus according to claim 1, and further comprising an oiling device disposed between the second pair of pressure rollers and the wind-up bobbin. 

1. Apparatus for forming sized slivers or rovings, said apparatus comprising, in combination: a. a frame; b. a feed bobbin for slivers or rovings mounted for free rotation substantially without friction in said frame; c. a vat of size; d. a first pair of pressure rollers mounted between said feed bobbin and said vat; e. a second pair of pressure rollers mounted downstream of said vat of size; f. a drier mounted downstream of said second pair of rollers; g. a windup bobbin positioned to receive the slivers or rovings from said drier; and h. a drive means effective to drive at least one of the rollers of each of said pairs of pressure rollers at a controlled speed.
 2. Apparatus as claimed in claim 1, wherein said drier comprises a cabinet, at least two superposed sets of return pulleys within said cabinet rotatable on substantially parallel axes, the pulleys of one set being mounted on the same shaft and being located in the same vertical plane as the pulleys of the other set.
 3. Apparatus as claimed in claim 1, and further comprising a support and transport filament for the slivers or rovings, means disposed between the feed bobbin and the first pair of pressure rollers for placing the support and transport filament into contact with the slivers or rovings and means to separate the sized slivers or rovings from the support and transport filament within the drier before the slivers or rovings are dry.
 4. Apparatus as claimed in claim 3, wherein said means for placing the slivers or rovings in contact with the support and transport filament comprise a frustoconical yarn guide having a larger and a smaller base, the larger base being directed towards the feed bobbin and the smaller base towards the first pair of said pressure rollers.
 5. Apparatus according to claim 3, wherein the means for separating the sized slivers or rovings from the support and transport filament within the drier comprise a rewind bobbin for the support and transport filament.
 6. Apparatus according to claim 3, wherein the support and transport filament is endless.
 7. Apparatus according to claim 1, and further comprising a pressure regulator associated with one of the rollers of each pair of pressure rollers, the other roller being mounted on a shaft having a fixed bearing.
 8. Apparatus according to claim 7, wherein the pressure regulator comprises a pair of levers, one lever being associated with each pair of pressure rollers, the lever being pivoted and carrying a bearing for said one roller of each pair and supporting an adjustable weight movable along its length.
 9. Apparatus according to claim 1, wherein said frame is itself mounted for rotation about an axis perpendicular to the axis of the feed bobbin.
 10. Apparatus according to claim 2, wherein the pulleys of the drier comprise a roller provided with axially spaced apart annular grooves of the same depth.
 11. Apparatus according to claim 1, and further comprising an oiling device disposed between the second pair of pressure rollers and the wind-up bobbin. 